Bifurcated endoluminal prosthesis

ABSTRACT

An introducer for delivering into the vasculature a straight or bifurcated stent or prosthesis; a method for delivering into the vasculature a straight or bifurcated stent or prosthesis; a method of treating and angeological disease using a bifurcated stent; an endoluminal stent having perpendicular hoop members, each hoop member formed of wire in a sinuous configuration, at least some of juxtaposed apices in neighboring hoops being secured to one another, such stents also forming axially aligned segments in straight stents, and segments of bifurcated stents in particular embodiments. Certain embodiments of such stents also include barbs, fabric covering and radiopaque markers.

[0001] This is a continuation-in-part application of the application ofcommon assignment herewith of inventors George Goicoechea, ClaudeMialhe, John Hudson and Andrew Cragg, entitled BIFURCATED ENDOLUMINALPROSTHESIS, filed on Sep. 27, 19941 for which application a serialnumber had not yet been assigned as of the date of filing thiscontinuation-in-part application.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a bifurcated endoluminalprosthesis for use in a bifurcated blood vessel such, for example, asthe infrarenal portion of a mammalian aortic artery where it bifurcatesto the common iliac arteries. The present invention also embraces astent connecting means for connecting a stent (e.g. a stent which formspart of an endoluminal prosthesis) to another stent, as well asapparatus and method for introducing prostheses to the vasculature andmethods of treating angeological diseases.

[0003] A stent is used to provide a prosthetic intraluminal wall e.g. inthe case of a stenosis to provide an unobstructed conduit for blood inthe area of the stenosis. An endoluminal prosthesis comprises a stentwhich carries a prosthetic graft layer of fabric and is used e.g. totreat an aneurysm by removing the pressure on a weakened part of anartery so as to reduce the risk of embolism, or of the natural arterywall bursting. Typically, a stent or endoluminal prosthesis is implantedin a blood vessel at the site of a stenosis or aneurysm by so-called“minimally invasive techniques” in which the stent is compressedradially inwards and is delivered by a catheter to the site where it isrequired through the patient's skin or by a “cut down” technique inwhich the blood vessel concerned is exposed by minor surgical means.When the stent is positioned at the correct location, the catheter iswithdrawn and the stent is caused or allowed to re-expand to apredetermined diameter in the vessel.

[0004] U.S. Pat. No. 4,886,062 discloses a vascular stent whichcomprises a length of sinuous or “zig-zag” wire formed into a helix; thehelix defines a generally cylindrical wall which, in use, constitutes aprosthetic intraluminal wall. The sinuous configuration of the wirepermits radial expansion and compression of the stent; U.S. Pat. No.4,886,062 discloses that the stent can be delivered percutaneously andexpanded in situ using a balloon catheter.

[0005] U.S. Pat. No. 4,733,665 discloses an expandable intraluminalgraft which is constituted by a tubular member formed from a pluralityof intersecting elongate members which permit radial expansion andcompression of the stent.

[0006] EP-A-0556850 discloses an intraluminal stent which is constitutedby a sinuous wire formed into a helix; juxtaposed apices of the wire aresecured to one another so that each hoop of the helix is supported byits neighboring hoops to increase the overall strength of the stent andto minimize the risk of plaque herniation; in some embodiments the stentof EP-A-0556850 further comprises a tubular graft member to form anendoluminal prosthesis.

[0007] The prior art stents and prostheses mentioned above are generallysatisfactory for the treatment of aneurysms, stenoses and otherangeological diseases at sites in continuous un-biurcated portions ofarteries or veins.

[0008] However, the prior art stents and prostheses are not whollysatisfactory for use where the site of desired application of the stentor prosthesis is juxtaposed or extends across a bifurcation in an arteryor vein such, for example, as the bifurcation in the mammalian aorticartery into the common iliac arteries. For example, in the case of anabdominal aortic aneurysm (“AAA”) in the infrarenal portion of the aortawhich extends into one of the common iliac arteries, the use of one ofthe prior art prosthesis referred to above across the bifurcation intothe one iliac artery will result in obstruction of the proximal end ofthe other common iliac artery; by-pass surgery is therefore required toconnect the one iliac artery in juxtaposition with the distal end of theprosthesis to the other blocked iliac artery. It will be appreciated bya person skilled in the art that it is desirable to avoid surgerywherever possible; the requirement for by-pass surgery associated withthe use of the prior art prosthesis in juxtaposition with a bifurcationin an artery therefore constitutes a significant disadvantage.

SUMMARY OF THE INVENTION

[0009] Throughout this specification, the term “proximal” shall mean“nearest to the heart,” and the term “distal” shall mean “furthest fromthe heart.”

[0010] According to one aspect of the present invention there isprovided a stent connecting means for connecting two intraluminal stentsone to the other to define a continuous lumen through the two stents,the stent connecting means including a first stent including a maleengaging portion which can be compressed radially inwardly, and a secondstent including a female cooperating portion. The male engaging portionmay be entered into the female cooperating portion in a radiallycompressed state and thereafter caused or allowed to expand in thefemale cooperating portion; the arrangement being such that in servicethe interengagement of the male engaging portion and the femalecooperating portion serves to resist longitudinal separation of the twostents one from the other.

[0011] Typically, the first stent may include a proximal male engagingportion; the second stent may include a distal female cooperationportion. The male engaging portion may be flared radially outwardlytowards its extremity, and the female cooperating portion may be taperedradially inwardly towards its extremity. In some embodiments, the maleengaging portion may comprise a frustoconical wall which flaresoutwardly towards its longitudinal extremity; the female engagingportion may comprise a frustoconical wall which tapers radially inwardlytowards its longitudinal extremity.

[0012] Alternatively, said male engaging and female cooperating portionsmay be substantially untapered; they may be substantially cylindrical.

[0013] The male engaging portion of the first stent may be resilientlycompressible in a radially inwards direction such that in the radiallycompressed state it is capable of self-reexpansion to engage in thefemale cooperating portion. Typically, each of said first and secondstents may be resiliently compressible.

[0014] In use therefore the second stent may be delivered in a radiallycompressed state by using a catheter; when the second stent is locatedat the site of use, the catheter may be withdrawn thereby allowing thesecond stent to re-expand to engage the endoluminal surface of the bloodvessel.

[0015] The first stent may then be delivered percutaneously or by a “cutdown” technique to a site distal of the second stent such that the maleengaging portion of the first stent in the radially compressed state isentered into the expanded female cooperating portion of the secondstent; the catheter may then be withdrawn allowing the first stent tore-expand such that the male engaging portion engages in the femalecooperating portion of the second stent.

[0016] In some embodiments of the present invention the second stent mayhave two transversely spaced distal female cooperating portions; thesecond stent may therefore constitute a bifurcated stent for use injuxtaposition with a bifurcation in a blood vessel.

[0017] Each of the two transversely spaced distal female cooperatingportions may be adapted for connection to a first male stent which, inuse, extends across the bifurcation into a respective one of thebranched blood vessels.

[0018] In a particular aspect of the present invention there is provideda bifurcated intraluminal stent for use in juxtaposition with anangeological bifurcation; the bifurcated intraluminal stent comprising aproximal portion adapted to be positioned in service in a blood vesselin juxtaposition with a bifurcation, a first distal stent portionadapted to extend across the bifurcation into one of the branched bloodvessels and a second distal stent portion adapted to allow blood to isflow from the proximal portion into the other branched vessel. The firstdistal stent portion may be formed integrally with the proximal portion.

[0019] In some embodiments the second distal stent portion may comprisea female cooperating portion which is adapted to engage a male engagingportion of a another stent adapted to extend in the other branched bloodvessel such that, in use, the bifurcated stent can be connected in situto the other stent. The bifurcated intraluminal stent may thereforeconstitute a second stent in accordance with the present inventioncomprising a distal female cooperating portion disposed intermediate theproximal and distal extremities of the stent; the other stent mayconstitute a first stent in accordance with the present invention.

[0020] Typically, the proximal end of said second stent may be flaredradially outwardly towards its extremity to engage the endoluminalsurface of the artery thereby to resist longitudinal movement of thesecond stent in service.

[0021] Each of the first and second stents may comprise a sinuous wireformed into a tubular configuration. The sinuous and tubularconfigurations may be imparted to the wire by winding it on a mandrel.Typically, each stent may be made from a shape memory nitinol(nickel-titanium) wire which may be wound on to the mandrel to form thestent in a tubular configuration of slightly greater diameter than thediameter of the blood vessel in which the stent is intended to be used.The stent may be annealed at an elevated temperature and then allowed tocool in air so that the nitinol wire “remembers” the configuration inwhich it was wound on the mandrel.

[0022] Said nitinol wire may be type “M” nitinol wire which ismartersitic at temperatures below about 13° C. and is austenitic attemperatures above about 25° C.; it will be appreciated therefore thatthe type “M” wire will be austenitic at body temperature of 37° C.Typically, the annealing may be conducted at about 500° C. or more forat least about 60 minutes; after cooling the wire may be immersed incold water to facilitate removal of the wire from the mandrel with thewire in its maleable martensitic form. Typically, the cold water mayhave temperature of less than about 10° C.; the wire may be immersed forabout 5 minutes or more. An advantage of using nitinol wire to form thestent in accordance with the present invention is that the nitinol wireis “super elastic” in its austenitic state; the radial outward forceexerted by the stent on the wall of the blood vessel in use is thereforesubstantially constant irrespective of the diameter of the vessel andthe expanded stent.

[0023] In some embodiments the wire may have a helical configuration asdisclosed in EP-A-0556850. Alternatively, the wire may be of an entirelynovel configuration, namely one in which the wire forms a plurality ofhoops such that the plane of the circumference of each hoop issubstantially perpendicular to the longitudinal axis of the scent. Eachhoop may comprise a substantially complete turn of the wire having asinuous configuration; optionally, as each hoop is completed, the pointof winding the wire may be displaced longitudinally with respect to thewinding axis to form the next hoop. When the next hoop is complete, thepoint of winding is moved further longitudinally with respect to thewinding axes to the form the next succeeding hoop and so on.

[0024] It will appreciated that an advantage of this novel arrangementis that the planes of the hoops are not skewed with respect to thelongitudinal axis of the stent; the longitudinal ends of the stent are“square”0 to said longitudinal axis, so that when the stent is caused orallowed to expand in situ there is substantially no twisting of thestent as it shortens in length. It will be appreciated that thisrepresents a significant advantage, as in areas of stenosis or aneurysmit is desirable to minimize the movement of the stent within the bloodvessel so as to reduce the potential trauma to the patient. A stent ofthis configuration may be used, apart from the bifurcated embodimentotherwise taught herein, in any application which in stents generallyhave heretofor been used.

[0025] Typically, the stents of this invention whether of the helical orperpendicular variety, also comprise a securing means for securing anapex of the sinuous wire in one hoop to a juxtaposed apex of aneighboring hoop so that each hoop is supported by its neighbors. Thesecuring means may comprise a loop element of a suture material, forexample, to tie the juxtaposed apices together; the loop element mayalso comprise a loop formed of a thermoplastics material such, forexample, as polypropylene. Alternatively, the securing means may be abead formed of a thermoplastic material around juxtaposed apices. Alsoalternatively, the securing means may be a loop, ring, or staple formedof wire such as nitinol.

[0026] The male engaging portion and female cooperating portion, of thefirst and second interengaging stents of this invention, may be formedseparately from the remainder of the respective nonengaging portions ofthese stents and then the engaging and non-engaging portions secured toone another by securing means.

[0027] In one embodiment of the present invention, the proximal anddistal stent portions of the bifurcated stent in accordance with thepresent invention may be formed separately; the distal end of theproximal stent portion may be secured to the wider proximal end of afirst intermediate frustoconical stent portion; the narrower distal endof the first intermediate frustoconical stent portion may be secured tothe proximal end of the distal stent portion. The female cooperatingportion of the bifurcated stent may be constituted by a secondfrustoconical stent portion which is secured to the distal end of theproximal stent portion in juxtaposition with the first frustoconicalportion.

[0028] Alternatively the first and second frustoconical portions may beomitted; the proximal and distal stent portions may be secured directlyone to the other.

[0029] The female cooperating portion may be constituted by a generallycylindrical stent portion secured to said proximal stent portion intransversely spaced relation to the distal portion.

[0030] Each of the first and second stents of the bifurcated form of thepresent invention may carry a tubular graft layer formed from abiocompatible fabric in juxtaposition with the stent; the combined stentand graft layer constituting an endoluminal prosthesis. Typically thegraft layer may be disposed externally of the stent; it will beappreciated however that in some embodiments the graft layer may bedisposed internally of the stent. In some embodiments the graft layermay be secured to the stent by loop elements such, for example, as loopsof polypropylene. The biocompatible fabric may be a polyester fabric ora polytetrafluoroethylene fabric; typically said fabric may be woven ora warp knitted polyester fabric. In some embodiments the woven or a warpknitted fabric may be formed in a seam-free bifurcated configuration asa sleeve for a bifurcated stent.

[0031] In some embodiments the male engaging portion of the first stentand the female cooperating portion of the second stent may be leftuncovered. Alternatively, the fabric graft layer may extend to theproximal extremity on the external surface of the male engaging portion,and may be folded over the distal extremity of the female engagingportion to form an inner sleeve; in use the external fabric of the maleengaging portion may butt against the folded over portion of the fabricinternally of the female cooperating portion to form a substantiallyblood tight seal.

[0032] The present invention in one aspect therefore includes abifurcated endoluminal prosthesis comprising a bifurcated stent inaccordance with the invention and a tubular graft layer.

[0033] The first stent having the male engaging portion may also have atubular graft layer. If required the first prosthesis may be introducedin a radially compressed state such that the male engaging portion ofthe first prosthesis is engaged in the intermediate female cooperatingportion of the bifurcated prosthesis; the first prosthesis is thencaused to be allowed to reexpand in situ such that the male engagingportion engages in the female cooperating portion to resist longitudinalseparation of the two prosthesis in service.

[0034] The bifurcated prosthesis may be adapted for use in theinfrarenal portion of a mammalian aorta in juxtaposition with thebifurcation of the common iliac arteries for the treatment of abdominalaortic aneurysms. In use the bifurcated endoluminal prosthesis may beintroduced into the infrarenal portion of the aorta using a cathetersuch that the first distal stent portion extends into one of thebranched iliac arteries; the catheter may then be withdrawn allowing theprosthesis to re-expand in situ.

[0035] It will be appreciated by a person skilled in the art that theprostheses may be introduced to the site of use percutaneously or by“cut down” techniques.

[0036] Any of the stents according to this invention may be provided onits external surface with circumferentially spaced wire barbs or hooksadapted to engage in the endoluminal surface of the host artery toresist longitudinal movement or slippage of the stent in use. Typicallythe barbs or hooks may be disposed on part of the stent which isprovided with a fabric graft layer such that in use the points of theartery which are engaged by the barbs or hooks are covered by the fabricgraft. It will be appreciated by a person skilled in the art that thetrauma to the artery wall caused by the hooks or barbs may cause emboli;the provision of the fabric graft over the barbs or hacks in use willtherefore help to prevent the introduction of such emboli into the bloodstream.

[0037] The male engaging portion for the first stent may be providedwith circumferentially spaced hooks or barbs on its external surface toengage the internal surface of said female cooperating means, thereby toreinforce the connecting means against longitudinal separation of thestents one from the other in the service.

[0038] The present invention therefore provides a connecting means forconnecting two stents longitudinally one to the other. It will beappreciated that this represents a significant step forward in the artas it allows the provision of a bifurcated endoluminal prosthesis foruse in juxtaposition e.g. with arterial bifurcations without requiringby-pass surgery to connect one of the branched arteries to the otherbranched artery.

[0039] In particular, the invention provides a bifurcated endoluminalprosthesis which can be positioned in an artery in juxtaposition with abifurcation to extend into one of the branched arteries; the bifurcatedprosthesis can be connected to another prosthesis which extends into theother branched artery. The prosthesis can be delivered percutaneously orby “cut down” methods and connected together in situ thereby to provideeffective treatment of an angeological disease such, for example, as ananeurysm or a stenosis which extends across a bifurcation in a bloodvessel without the need for by-pass surgery.

[0040] In another aspect, this invention provides an introducer fordelivering, into the vasculature at an angeological bifurcation where ablood vessel branches into two branched vessels, a bifurcatedendoluminal stent or prosthesis having a proximal portion adapted to bedisposed in the blood vessel and a distal portion adapted to be disposedat least partially in one of the two branched vessels. The introducercomprises a tubular outer sheath, a proximal portion pusher disposed atleast partially within the outer sheath, and a distal portion pusherdisposed at least partially within the proximal portion pusher.

[0041] The present invention further provides an introducer fordelivering into the vasculature at an angeological bifurcation where ablood vessel branches into two branched vessels, an endoluminalprosthesis having a proximal stent portion and a distal stent portion.The introducer comprises a tubular outer sheath, a proximal portionpusher disposed at least partially within the outer sheath and having aproximal end adapted to contact the proximal stent portion, a distalportion pusher disposed at least partially within the proximal portionpusher and having a proximal end adapted to contact the distal stentportion; and a balloon catheter, having a balloon attached thereto,disposed at least partially within the distal portion pusher.

[0042] This invention in another aspect provides a method for deliveringa bifurcated endoluminal stent or prosthesis having a proximal portionand a first distal portion into the vasculature at an angeolagicalbifurcation where a blood vessel branches into a first branched vesseland a second branched vessel. The method comprises inserting a firstintroducer containing the stent or prosthesis into the vasculature to apredetermined delivery location, the first introducer comprising anouter sheath, a proximal portion pusher, and a distal portion pusher;withdrawing the outer sheath of the first introducer while maintainingthe proximal portion pusher in a fixed position until the proximalportion of the stent or prosthesis is deployed from the first introducerinto the blood vessel; withdrawing the outer sheath and the proximalportion pusher while maintaining the distal portion pusher in a fixedposition until the first distal portion of the stent or prosthesis isdeployed from the first introducer at least partially into the firstbranched vessel; and withdrawing the first introducer from thevasculature.

[0043] This invention further provides a method for delivering, into thevasculature at an angeological bifurcation where a blood vessel branchesinto two branched vessels, an endoluminal prosthesis having a proximalstent portion, and a distal stent portion. The method comprises thesteps of inserting an introducer containing the prosthesis into thevasculature to a predetermined delivery location, the introducercomprising an outer sheath, a proximal stent portion pusher, a distalstent portion pusher, and a balloon catheter having a balloon attachedthereto; inflating the balloon to at least partially block blood flow inthe blood vessel; withdrawing the outer sheath of the introducer whilemaintaining the proximal stent portion pusher in a fixed position untilthe proximal stent portion of the prosthesis is deployed from theintroducer into the blood vessel; withdrawing the outer sheath and theproximal stent portion pusher while maintaining the distal stent portionpusher in a fixed position until the distal stent portion of theprosthesis is deployed from the introducer into the blood vessel; andwithdrawing the introducer from the vasculature.

[0044] In general, this invention provides a method of treating anangeological disease at a bifurcation site where a blood vessel branchesinto a first branched vessel and a second branched vessel comprising thesteps of disposing in the blood vessel a proximal portion of anendoluminal stent; directing blood flow from the blood vessel into thefirst branched vessel through a first distal portion of the endoluminalstent, the first distal portion being connected to the proximal portionand extending into the first branched vessel; and directing blood flowfrom the blood vessel into the second branched vessel through a seconddistal portion of the endoluminal stent, the second distal portion beingconnected to the proximal portion and extending into the second branchedvessel. This method may be amplied to aneurysms, occlusions, orstenosis.

[0045] Following is a description by way of example only and withreference to the accompanying drawings of the present invention,including novel stent constructions and methods of manufacture and usethereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The aspects, features and advantages of the present inventionwill be more readily understood from the following detailed descriptionwhen read in conjunction with the accompanying drawings, in which:

[0047]FIG. 1a is a front view of a bifurcated intraluminal stent inaccordance with the present invention constituting part of anendoluminal prosthesis.

[0048]FIG. 1b is a front view of another stent which is adapted to beconnected to the bifurcated stent of FIG. 1a.

[0049]FIG. 2(a) is a side view of part of the bifurcated stent of FIG.1a opened up to show its construction.

[0050]FIG. 2(b) is a side view of an exemplary mandrel used to form thepart of the bifurcated stent shown in FIG. 2(a).

[0051]FIG. 3 is a side view of another part of the bifurcated stent ofFIG. 1a opened up to show its construction.

[0052]FIG. 4(a) is a side view of yet another part of the bifurcatedstent of FIG. 1a opened up to show its construction.

[0053]FIG. 4(b)-4(f) are partial exploded views of the exemplary stentof FIG. 4(a) illustrating alternative means for securing juxtaposedapices according to the present invention.

[0054]FIG. 5 is a schematic perspective view of a bifurcated endoluminalprosthesis in accordance with the present invention.

[0055]FIG. 6 is a schematic view of another bifurcated endolurninalprosthesis in accordance with the present invention.

[0056]FIG. 7 is a schematic view of yet another bifurcated endoluminalprosthesis in accordance with the present invention.

[0057]FIG. 8(a) is a cross-sectional view of an exemplary assembledintroducer according to the present invention.

[0058] FIGS. 8(b)-8(e) are side views of the component parts of theintroducer of FIG. 8(a).

[0059]FIG. 8(f) is a partial cross-sectional view of the introducer ofFIG. 8(a).

[0060]FIG. 8(g) is a cross-sectional view of part of the introducer ofFIG. 8(f) taken along the line A-A.

[0061]FIG. 9 is a side cross-sectional view of a portion an alternativeembodiment of an introducer according to the present invention.

[0062] FIGS. 10(a) and 10(b) are side views of other alternativeembodiments of an introducer according to the present invention.

[0063]FIGS. 11 through 20 are sequential cross-sectional views of thebifurcation of the abdominal aortic artery during introduction of anexemplary prosthesis according to the present invention.

[0064] FIGS. 21(a)-21(c) are cross-sectional views of alternativeinsertion apparatus according to the present invention.

[0065]FIGS. 22 and 23 are side views of alternative stents according tothe present invention.

[0066] FIGS. 24(a), 24(b), 25, 26 and 27 are sequential cross-sectionalviews of the bifurcation of the abdominal aortic artery duringintroduction of an exemplary prosthesis according to the presentinvention.

[0067]FIGS. 28 and 29 are cross-sectional side views of alternativedelivery apparatus according to the present invention.

[0068] FIGS. 30-34 are sequential cross-sectional views of thebifurcation of the abdominal aortic artery during introduction of anexemplary prosthesis according to the present invention.

DETAILED DESCRIPTION

[0069] The present invention includes apparatus and method for treatingangeological diseases in any bifurcated blood vessel. One example ofsuch a bifurcated blood vessel is the infrarenal portion of a mammalianaortic artery where it bifurcates to the common iliac arteries. Examplesof diseases that can be treated using the apparatus and method of thepresent invention include aneurysm, stenosis, and occlusion.

[0070] A bifurcated stent in accordance with the present invention whichis indicated at 10 in FIG. 1a comprises a wire skeleton which isconstructed in four separate parts, namely a proximal part 12, a firstfrustoconical part 14, a first distal part 16 and a second frustoconicalpart 18. Said bifurcated stent 10 carries a fabric graft layer (FIGS. 5,6, and 7) for use as an endoluminal prosthesis e.g. in the infrarenalportion of a mammalian aorta in juxtaposition with the bifurcation ofthe common iliac arteries. It will be appreciated, however, thatbifurcated stents (with or without fabric graft layers) for use indifferent parts of the angeological system and for different mammals canbe constructed in accordance with the invention by varying thedimensions of the stent accordingly.

[0071] Each of the four parts of the bifurcated stent 10 is made insubstantially the same way by winding a shape memory nitinol wire,typically nitinol type M wire, onto a mandrel 46.

[0072] The construction of the exemplary proximal part 12 of thebifurcated stent 10 is shown in FIGS. 2(a) and 2(b); nitinol wire type Mwire typically having a diameter of 0.46 mm (0.018″) is wound aroundmandrel 46 to is form a plurality of hoops 20. The winding surface ofmandrel 46 is provided with a plurality of upstanding pins 47 disposedin a zig-zag pattern for each of the hoops 20 so that in each hoop 20the nitinol wire follows a sinuous path to define a plurality ofcircumferentially spaced apices 22. Each hoop 20 is wound onto mandrel46 such that the plane of the circumference of each hoop 20 issubstantially perpendiculaar to the longitudinal axis of the mandrel.

[0073] When one hoop 20 e.g. the hoop indicated at 20 a has been formed,the point of winding of the nitinol wire is displaced longitudinallywith respect to the axis of mandrel 46 to form the next successive hoop20 b. The stent shown in FIG. 2(a) is the stent formed on mandrel 46shown in FIG. 2(b) after cutting the stent longitudinally and rotatingit 45 degrees to show the construction of the stent.

[0074] The proximal part of the exemplary bifurcated stent of FIG. 1a isformed on the mandrel with a diameter of about 24 mm and a length in thelongitudinal direction of about 55 mm. From FIGS. 1(a), 2(a), and 2(b)it will be noted that the proximal part 12 is constituted by three hoops20 of unit width at the proximal end 24 of the proximal part 12, twointermediate hoops 25 of twice unit width and, at its distal end 26, bya single hoop 20 of unit width. In the illustrated embodiment,intermediate hoops 25 have a plurality of is offsets 25 a. Offsets 25 aare formed when the wire is passed around pins 47 on mandrel 46. Offsets25 a add stability to the stent. When the nitinol wire has been woundonto mandrel 46, the nitinol wire is annealed at an elevated temperatureand then allowed to cool.

[0075] In this embodiment of the invention the wire is annealed at atemperature of about 500° C. for 60 minutes and is then allowed to coolin air. The purpose of the annealing is so that the nitinol wire in itsaustenitic form “remembers” its configuration as wound on mandrel 46; itwill be appreciated therefore that other temperatures and durations forthe annealing are included within the present invention provided thenitinol wire “remembers” its wound configuration.

[0076] After annealing and cooling, the wire is immersed in cold waterat less than 10° C. for about 5 minutes; the wire is then removed fromthe mandrel, and juxtaposed apices 22 of neighboring hoops 20 aresecured together by securing means 99 (see FIG. 4(a)), which are, inthis example, 0.003″ polypropylene filaments. Each apex 22 of each hoop20 which has a juxtaposed apex of a neighboring hoop 20 is tied to thejuxtaposed apex 22. It will be appreciated, however, that in otherembodiments of the invention only some of the juxtaposed apices 22 maybe secured in this way.

[0077] In addition to polypropylene filaments, the securing means maycomprise a loop element 99 a of a suture material, for example, to tiethe juxtaposed apices together, as shown in FIG. 4(b). The securingmeans may also comprise bead 99 b formed of a thermoplastic materialaround juxtaposed apices, as shown in FIG. 4(c). Also alternatively, thesecuring means may be a loop 99 c, ring 99 d, or staple 99 e formed ofwire such as nitinol, as shown in FIGS. 4(d), 4(e), and 4(f)respectively.

[0078] The exemplary first and second frustoconical parts 14, 18 of theskeleton shown in the figures are formed in substantially the same wayas the proximal part 12 by winding nitinol wire onto a mandrel and thenannealing the wire before removing it from the mandrel. As shown in FIG.3, the first and second frustoconical parts 14, 18 are each constitutedby three hoops 20 of unit width. The mandrel is tapered such that theproximal end of each of the exemplary frustoconical parts 14, 18 isformed with a diameter of about 12 mm and the distal end 32 of each isformed with a diameter of about 9 mm. The overall length of each of theexemplary frustoconical parts 14, 18 is about 18 mm. The wire used forthe frustoconical parts 14, 18 is nitinol type M wire having a diameterof 0.28 mm (0.011″). Juxtaposed apices 22 of each of the exemplaryfrustoconical parts 14, 18 are tied together using 0.03″ polypropylenefilaments as described above. The first and second frustoconical parts14, 18 are secured to the distal end 26 of the proximal part 12 of thestent 10 in transversely spaced relation as shown in FIG. 1a by securingthe apices 22 of the hoop 20 forming the wider proximal end 30 of eachof the frustoconical parts 14, 18 to juxtaposed apices 22 of the hoop 20on the distal end 26 of the proximal part 12.

[0079] The exemplary first distal part 16 of the bifurcated stent 10 isformed by winding nitinol type M wire typically having a diameter of0.28 mm (0.011″) onto a mandrel to form twelve longitudinally spacedhoops 20 as shown in FIG. 4; the exemplary first distal part has anoverall length of about 66 mm and a uniform diameter of about 9 mm. Theproximal end 34 of the distal part 16 is secured to the narrower distalend 32 of the first frustoconical part 14 by tying each apex 22 on theproximal end 34 of the first distal part 16 to a juxtaposed apex on thedistal end 32 of the first frustoconical part 14 using, in thisembodiment, 0.003″ polypropylene filaments.

[0080] The proximal part 12, the first and second frustoconical parts14, 18, and the first distal part 16 are each covered with a tubulargraft layer of a biocompatible woven fabric (FIGS. 5, 6, and 7) such,for example, as a plain woven fabric made from 30 or 40 denierpolyester. The tubular fabric layers may be attached to the proximal anddistal parts 12, 16 of the stent 10 by stitching with, for example,0.003″ polypropylene filaments around the apices 22 of the underlyingskeleton. The fabric covered stent constitutes one form of anendoluminal prosthesis.

[0081] The proximal part 12 of the wire skeleton may be provided with aplurality of circumferentially spaced hooks or barbs 43 which projectthrough the tubular fabric layer to engage in the endoluminal surface ofa host artery in service.

[0082] The sinuous configuration of each turn 20 of the wire skeleton ofthe stent 10 allows the prosthesis to be compressed resiliently radiallyinwards so that it can be received in a catheter e.g. a 16 or 18 Frenchcatheter for percutaneous or cut down delivery, e.g. to an intraluminalsite in the infrarenal section of the aortic artery. Larger diametercatheters up to, e.g., 20 French, may be used to deliver the prosthesisusing “cut down” procedures.

[0083] An x-ray opaque marker may be attached to one or more ends of astent so that the delivery of the stent can be monitored using x-rays.As shown in FIG. 4(a), such a radiopaque marker may typically comprise agold or platinum wire 17 crimped onto an end of stent 16. Alternatively,the radiopaque marker may be a tube 17 a disposed around a length ofwire on the stent, also as shown in FIG. 4(a). Typically, in thebifurcated stent the marker is secured to the stent in line with thedistal stent portion so that the distal stent portion can be alignedwith and inserted into one of the branched arteries in situ.

[0084] The bifurcated endoprosthesis is positioned in the infrarenalsection of the aortic artery in juxtaposition with the bifurcation ofthe common iliac arteries such that the first distal part 16 of theprosthesis extends into one of the common iliac arteries. The catheteris then withdrawn allowing the stent 10 to re-expand towards itsconfiguration as wound on the mandrel in which it was annealed until thestent engages the endoluminal surface of the host artery. The barbs orhooks engage the endoluminal surface of the host artery to resistlongitudinal displacement or slipping of the prosthesis in use.

[0085] It will be apreciated that when the bifurcated prosthesis ispositioned and re-expanded in the fitted position, blood can flow fromthe aortic artery into the proximal cart 12 of the prosthesis from whereit can flow into the one common iliac artery through the frustoconicalpart 14 and the first distal part 16 and also into the other commoniliac artery through the second frustoconical part 18.

[0086] In cases where it is required to implant a prosthesis in theother common iliac artery a second prosthesis comprising a second stent40 as shown in FIG. 1b can be used. The second stent 40 includes a wireskeleton comprising a proximal frustoconical part 42 and a distal part44. The distal part 44 of the second stent 40 also may be covered with atubular graft layer of a biocompatible fabric such, for example, aspolyester or polytetrafluoroethylene fabric (FIGS. 5, 6, and 7).

[0087] The frustoconical proximal part 42 is constructed in the same wayas the frustaconical parts 14, 18 of the bifurcated stent 10; the distalpart 44 is constructed in the same way as the distal part 16 of thebifurcated stent 10. The distal end of the frustoconical proximal part42 is secured to the proximal end of the distal part 44 by securingjuxtaposed apices using polypropylene filaments as described above.

[0088] In use, the second prosthesis is compressed radially inwards andis received in a catheter for percutaneous or “cut down” delivery to theother common iliac artery. The frustoconical proximal part 42 is guided,in the radially compressed state, into the second frustoconical part 18of the bifurcated stent 10. The catheter is then withdrawn allowing thesecond stent 40 to re-expand towards its remembered configuration, untilthe distal part 14 engages the endoluminal surface of the other commoniliac artery, and the outer surface of the frustoconical proximal part42 engages the interior surface of the second frustoconical part 18 ofthe bifurcated stent 10.

[0089] As with other stents described herein, the frustoconical proximalpart 42 may be formed with circumferentially spaced barbs or hooks 43,as shown in FIG. 1b, which engage in the wire skeleton of the secondfrustoconical part 18 of the bifurcated stent 10. When barbs 43 are onproximal portion 12, they engage the inner wall of the artery.

[0090] The tapered configurations of the second frustoconical part 18 ofthe bifurcated stent 10 and of the proximal frustoconical part 42 of thesecond stent 40 are such that in the fitted position as described, theprosthesis are locked together to resist longitudinal separation inservice. Barbs or hooks on the second stent 40 and/or an frustoconicalproximal part 42 help to resist such longitudinal separation.

[0091] In another example of the present invention a bifurcatedendoluminal prosthesis 50 as shown in FIG. 5 includes a bifurcated stentcomprising a proximal portion 52 which tapers radially inwardly from itsproximal end 54 to its distal end 56, and first and second transverslyspaced frustoconical distal portions 58, 60 which are secured to thedistal end 56 of the proximal portion 52; the proximal portion 52 iscovered with a tubular graft layer of a biocompatible fabric 62.

[0092] In use the prosthesis is delivered percutaneously or by “cutdown” methods to an artery in juxtaposition with an arterialbifurcation; blood can flow through the frustoconical proximal portion52 into each of the branched arteries through the first and seconddistal frustoconical portions 58, 60. If a prosthesis is required in oneor both of the branched arteries, a separate prosthesis comprising astent of the type shown in FIG. 1b referred to above covered with fabriccan be connected to the bifurcated prosthesis 50 by inserting andre-expanding the proximal end of such a separate prosthesis in one orboth of the distal frustoconical portions 58, 60 of the prosthesis 50for engagement therein.

[0093] Another variant of the present invention is shown in FIG. 6 whichshows a bifurcated endoluminal prosthesis 70 having a proximal portion72 which is secured at its distal end 74 to two transversely spacedfrustoconical intermediate portions 76, 78.

[0094] One of said frastoconical intermediate portions 76 is secured atits distal end to an elongate distal portion go. The proximal end 82 ofthe proximal portion 72 is flared radially outwards towards its proximalend 82 to engage the intraluminal surface of the host blood vessel inservice. Save for this flared portion, the entire endoprosthesis iscovered with a fabric graft layer as shown in FIG. 6; said graft layeris carried externally of the wire skeleton and is folded over the distalextremity 84 of the other frustoconical intermediate portion 78 to forman internal lining in said other frustoconical immediate portion 78.

[0095] Said other frustoconical intermediate portion 78 constitutes afemale cooperating portion in accordance with the present inventionwhich is adapted to receive a male engaging portion of anotherprosthesis as indicated at 86 in FIG. 6. Said other prosthesis 86includes a frustoconical proximal portion 88 which constitutes the ismale engaging portion and an elongate distal portion 90. The whole ofthe other prosthesis 86 is covered with a fabric graft layer as shown inFIG. 6. In service, the male engaging portion 88 of the other prosthesis86 is entered into and engaged with the female cooperating portion 78 ofthe bifurcated prosthesis 70 in situ in the manner herein beforedescribed. The fabric layer on the male engaging portion 88 buttsface-to-face on the folded over portion of the fabric layer disposedinternally of the female cooperating portion 78 to form a substantiallyblood-tight seal therewith.

[0096] Yet another example of the present invention is shown in FIG. 7in which a bifurcated endoluminal prosthesis 91 has a generallycylindrical proximal portion 92; said proximal portion 92 is connectedat its distal end 93 to an elongate, generally cylindrical distalportion 94. Said proximal portion 92 is also connected at its distal end93 to a generally cylindrical intermediate portion 95 which is securedin transversely spaced relation to the elongate distal portion 94. Saidcylindrical intermediate portion 95 constitutes a female engagingportion which is adapted to receive a generally cylindrical maleengaging portion of a second elongate prosthesis (not shown). The maleengaging portion is equipped with circumferentially spaced externalbarbs to engage in the female cooperating portion in service. As shownin FIG. 7, the whole of the bifurcated prosthesis 91 is covered with anexternal fabric graft layer save for a flared portion 96 towards theproximal end 97 of the proximal portion 92.

[0097] Referring to FIGS. 8(a)-8(f), an exemplary embodiment of adelivery system according to the present invention will be described.This system is used to deploy the bifurcated stent 10 when it is coveredwith a fabric graft layer to create an endoluminal prosthesis.Introducer 100 includes outer sheath 101. Outer sheath 101 is acylindrical tube adapted to be inserted either percutaneously or by“cut-down” procedures into the vasculature from an entry point to thebifurcation site where the prosthesis is to be deployed.

[0098] Housed within outer sheath 101 is proximal portion pusher 102.Proximal portion pusher 102 is a cylindrical tube having an outsidediameter smaller than the inside diameter of outer sheath 101. Proximalportion pusher 102 is preferably slidable throughout the length of outersheath 101.

[0099] Disposed within proximal portion pusher 102 is distal portionpusher 103. Distal portion pusher 103 is a cylindrical tube slidablycontained within distal portion pusher 102. Distal portion pusher 103 ispreferably adapted to slide throughout the entire length of proximalportion pusher 102.

[0100] Disposed within distal portion 103 is balloon catheter 104.Balloon catheter 104 is adapted to slide within distal portion pusher103. At the leading end 105 of balloon catheter 104 is nose cone 106.Balloon 107 is is attached to balloon catheter 104 between nose cone 106and proximal end 115 of proximal portion pusher 102.

[0101] As shown in FIG. 8(g), which is a cross-sectional view of ballooncatheter 104 in the direction A-A of FIG. 8(f), balloon catheter 104 hasa guide wire 20 conduit 104 a. Guide wire conduit 104 a extendsthroughout the length of balloon catheter 104 for passing a guide wire(not shown) through introducer 100. In the illustrated embodiment,balloon catheter 104 also includes injection orifice 109 and aninjection conduit 109 a. Injection conduit 109 a connects injectionorifice 109 to an injection site 108 at or near the distal end ofballoon catheter 104 as shown in FIG. 8(e). Radiopaque liquid may beinjected into injection site 108, through injection conduit 109 a, outinjection orifice 109, and into the vasculature to monitor deployment ofthe prosthesis.

[0102] Also in the illustrated embodiment of FIGS. 8(f) and 8(g),balloon catheter 104 has an inflation orifice 110 located at a pointwhere balloon 107 is attached to balloon catheter 104. A ballooninflation conduit 110 a connects balloon inflation orifice 110 toballoon inflation site 111 (FIG. 8(e)). Balloon 107 may be inflated anddeflated from balloon inflation site 111 during delivery of theprosthesis.

[0103] In an alternative embodiment illustrated in FIG. 9, seals 150,151 may be disposed around the distal is 15 ends 160, 161 of outersheath 10 and proximal portion pusher 102. Seals 150, 151 may be formedof silicone tubes.

[0104]FIG. 10(a) shows an alternative embodiment of introducer 100. Asshown in FIG. 10(a), wings 112 and 113 are provided at the distal end ofintroducer 100. Wing 112 is connected to proximal portion pusher 102,and wing 113 is connected to outer sheath 101. Wings 112 and 113indicate the rotational orientation of proximal portion pusher 102 andouter sheath 101, respectively. This in turn indicates the orientationof proximal portion 12 within outer sheath 101 and distal portion 16within proximal portion pusher 102. Wings 112 and 113 in the illustratedembodiment are also provided with holes 112 a and 113 a.

[0105] As shown in FIG. 10(b), a rod 128 or other fixation device may beattached to wings 112 and 113 using e.g. bolts through holes 112 a and113 a secured by wing nuts 129 or other securing means. Rod 128 preventsrelative movement of proximal portion pusher 102 and outer sheath 101.Wings may also be provided on distal portion pusher 103 and used tosecure distal portion pusher 103 to either proximal portion pusher 102or outer sheath 101 using a fixation device as described above.

[0106] Also shown in FIG. 10(a) as part of introducer 100 is hemostasisvalve 114. Hemostasis valve 114 is connected to distal portion pusher103 and acts as a simple seal around balloon catheter 104. Although itprevents fluid loss, hemostasis valve 114 allows balloon catheter 104 toslide within distal portion pusher 103. Alternatively, a Touhy-Borstvalve (not shown) may be used instead of hemostasis valve 114. TheTouhy-Borst valve is a device that may be manually tightened overballoon catheter 104. Lightly tightening such a valve permits ballooncatheter 104 to slide; firmly tightening such a valve clamps ballooncatheter 104 in place.

[0107] In use, the prosthesis must first be loaded into introducer 100.Cuter sheath 101 is first removed from introducer 100. Balloon catheter104 is then threaded through digital portion 16 and proximal portion 12of the prosthesis. The prosthesis is then cooled to a temperature ofapproximately 10° C. or below and radially compressed. For this purpose,the prosthesis may be immersed in cold water. The prosthesis shouldpreferrably remain in the water during the loading operation.

[0108] As supporting stent 10 is compressed beneath the fabric coveringof the prosthesis, excess fabric is produced. This excess fabric maysimply be pinched together and laid over the compressed prosthesis inlongitudinal folds.

[0109] Distal portion 16 of the prosthesis in the radially compressedstate is then inserted into proximal portion pusher 102. Outer sheath101 is then pulled over proximal portion 12 of the prosthesis and overproximal portion pusher 102. A thread (not shown) may be attached to theproximal end of proximal portion 12 of the prosthesis and threadedthrough outer sheath 101. This thread may then be used to pull proximalportion 12 through outer sheath 101. During the loading process, it isimportant to keep proximal portion 12 and distal portion 16 of theprosthesis properly aligned with outer sheath 101 and proximal portionpusher 102. Marks may be placed on the outside of outer sheath 101 andproximal portion pusher 102 to ensure proper alignment.

[0110] Referring again to FIG. 8(f), the prosthesis is inserted suchthat the outer surface of proximal portion 12 contacts and is radiallyrestrained by outer sheath 101, and the outer surface of distal portion16 contacts and is radially restrained by proximal portion pusher 102.End 115 of proximal portion pusher 102 longitudinally engages proximalportion 12 of the prosthesis as shown in FIG. 8(f).

[0111] Balloon catheter 104 is positioned such that nose cone 106 justclears proximal end 117 of outer sheath 101. The introducer is now incondition for insertion into the patient.

[0112] Referring to FIG. 11, introducer 100 is passed through an entrypoint (not shown) either in the patient's skin (percutaneous operation)or into the vasculature itself which has been surgically exposed(“cut-down” operation). Introducer 100 is inserted over a guide wire 170into the vasculature from the entry point to the desired deliverylocation at an angeological bifurcation.

[0113] In the aorta, introducer 100 is positioned such that end 117 ofouter sheath 101 is approximately level with renal arteries 180 as shownin FIG. 11. Balloon catheter 104 is then extended while maintainingouter sheath 101 in a fixed position. Balloon catheter 104 in thisembodiment is extended until distal end 105 of nose cone 106 isapproximately 35 mm above the proximal tip 117 of outer sheath 101.Then, while maintaining proximal portion pusher 102 in a fixed position,outer sheath 101 is withdrawn until the proximal tip of the prosthesisis level with proximal tip 117 of outer sheath 101. It will be notedthat balloon catheter 104 does not move while outer sheath 101 is sowithdrawn.

[0114] Introducer 100 is then repositioned to place the prosthesis inthe desired deployment location. Proper placement may be facilitatedwith the use of radiopaque markers as described above. Balloon catheter104 is then extended such that balloon 107 is above renal arteries 180.Balloon 107 is then inflated to occlude the aorta as shown in FIG. 12.

[0115] While maintaining proximal portion pusher 102 in a fixedposition, outer sheath 101 is withdrawn until the proximal end of theprosthesis emerges from outer sheath 101 as shown in FIG. 13. Using aradiopaque marker 120 disposed on proximal end of the prosthesis, theintroducer is rotated until proper alignment of the prosthesis isobtained. In the illustrated embodiment, radiopaque marker 120 is aplatinum wire twisted around an apex of the prosthesis in a “V” shape.To ensure proper alignment, the stent should be rotated until only theprofile of the V is seen and shows up as a straight line rather than a“V”.

[0116] Outer sheath 101 is further withdrawn while maintaining proximalportion pusher 102 fixed until proximal portion 12 is fully deployedfrom the end of outer sheath 101, and the frustoconical portion 1 of theprosthesis just clears end 117, as shown in FIG. 14.

[0117] Balloon 107 is then deflated to allow blood to flow throughproximal portion 12 and out frustoconical portion 16 of the prosthesis.Balloon 107 is withdrawn into the prosthesis until the distal end 118 ofnose cone 106 is just above the proximal end of the prosthesis.

[0118] Balloon 107 is then inflated to seat the prosthesis, which may beprovided with barbs (not shown) at its proximal end, against the wall ofthe aorta, as shown in FIG. 15.

[0119] Distal portion pusher 103 is then maintained in a fixed positionwhile outer sheath 101 is withdrawn. Once outer sheath 101 has beenwithdrawn to the point at is which proximal end 117 of outer sheath 101is flush with proximal end 115 of proximal portion pusher 102, bothouter sheath 101 and proximal portion pusher 102 are withdrawn, stillmaintaining distal portion pusher 103 in a fixed position. Outer sheath101 and proximal portion pusher 102 are withdrawn until distal portion16 of the prosthesis is deployed clear of proximal end 116 of distalportion pusher 103 as shown in FIG. 16. Balloon 107 is slowly deflatedto allow blood flow to be established through the proximal portion 12 ofthe prosthesis and out through frustoconical portion 18. Balloon 107 maybe used to model distal portion 16 of the prosthesis as necessary byinflating balloon 107 where needed to expand distal portion 16. Balloon107 is then deflated, and introducer 100 is withdrawn from thevasculature, leaving the guide wire 170 in place, as shown in FIG. 17.

[0120]FIG. 21(a) illustrates an exemplary second S introducer 300 usedfor deploying second distal part 44. Second introducer 300 of theillustrated embodiment comprises cylindrical outer sheath 301 and femaleLuer lock assembly 310. Second introducer 300 also has hemostasis valve361 contained within a hub 362 thereof. Cartridge 311 shown in FIG.21(b) is adapted to be attached to second introducer 300. Cartridge 311has threaded male Luer lock assembly 312 provided on its proximal end.Cartridge 311 has outer tube 313 which houses inner tube 314.

[0121] In use, a thin-walled tube (not shown) is first threaded throughdistal portion 44. This tube serves as a guide wire guide, allowing aguide wire to be threaded straight through distal portion 44 asdiscussed below. Distal portion 44 containing the thin-walled tube isthen cooled, radially compressed, and inserted into inner tube 314 ofcartridge 311 in a manner similar to that described for inserting thebifurcated prosthesis into proximal portion pusher 102 and outer sheath101. When distal portion 44 has been loaded into inner tube 314 ofcartridge 311, the thin-walled tube serving as a guide wire guideextends out both ends of cartridge 311.

[0122] A guide wire 171 is then inserted into the vasculature to thebifurcation site and through distal stent portion 12 as shown in FIG.18. A dialator 359 (FIG. 21(c)) having an outer diameter slightly lessthan the inner diameter of second introducer 300 is then inserted intosecond introducer 300 such that tapered end 360 extends out end 320 ofsecond introducer 300. End 360 of dialator 359 has a hole therein thatis just slightly larger than guide wire 171 and tapers gradually outwardfrom the hole to the outer diameter of dialator 359.

[0123] Second introducer 300 is then inserted into the vasculature overguide wire 171 by passing guide wire 171 into and through dialator 359.Dialator 359 with tapered end 360 provides a smooth transition withinthe blood vessel from the diameter of guide wire 171 to the diameter ofsecond introducer 300. Second introducer 300 is maneuvered such thatouter sheath 301 is inside frustoconical portion 18 of proximal portion12 by at least 20 mm in this embodiment, as shown in FIG. 19. Dialator359 is then removed from second introducer 300 and from the vasculatureand is discarded.

[0124] Cartridge 311 is then passed over guide wire 171 by passing guidewire 171 through the thin-walled guide wire guide within distal portion44 contained in cartridge 311. The guide wire guide is then removed anddiscarded.

[0125] Cartridge 311 is then lockingly engaged with introducer 300 bymating male Luer lock assembly 310 with female Luer lock assembly 312.Such locking engagement prevents relative movement of cartridge 311 andintroducer 300. Preventing relative movement lends stability andreliability to the insertion process that has not heretofore beenachieved.

[0126] A pusher 315 is then inserted into inner tube 314 of cartridge311 such that proximal end 317 of pusher 315 longitudinally contacts adistal end of distal portion 44 within inner tube 314. Pusher 315 pushesdistal portion 44 through cartridge 311 and into outer sheath 301 ofintroducer 300. Distal portion 44 is pushed through outer sheath 301,which remains in a fixed position, until distal portion 44 is atproximal end 320 of outer sheath 301 (see FIG. 19). Again, radiopaquemarkers 120 may be used to align distal portion 44 properly withproximal portion 12.

[0127] Pusher 302 is held firmly in place, and outer sheath 301 iswithdrawn approximately 2 cm. This deploys frustoconical part 42 ofdistal part 44 inside the frustoconical part 18 as shown in FIG. 19. Theouter surface of frustoconical part 42 engages the inner surface offrustoconical part 18 such that distal portion 44 is connected toproximal portion 12 to resist longitudinal separation.

[0128] Cuter sheath 301 may then be withdrawn while maintaining pusher302 in a fixed position to fully deploy distal portion 44, as shown inFIG. 20. If necessary, balloon catheter 104 may be inserted throughsheath 301 in order to model distal portion 44. Introducer 301 and guidewires 170, 171 are then removed from the vasculature and the entrypoints are closed.

[0129] The delivery apparatus and method described above areparticularly useful in treating an abdominal aortic aneurysm with abifurcated prosthesis according to the present invention. Other diseasesand alternative embodiments of the prosthesis and delivery method willnow be described.

[0130] In the case of an abdominal aortic aneurysm confined to the aortaand not extending far enough to affect the iliac arteries, a straight(i.e. nonbifurcated) stent may be used. Preferably, for suchapplications, the straight stent comprises a composite of at least twoaxially aligned stent segments. Two embodiments of such straight stentsare described herein, each comprising axially aligned stent requests,each of the requests comprising one or more adjacent hoops,perpendicular to a common axis, and each hoop being formed of wire in asinuous or zigzag configuration with some or all of the juxtaposedapices in adjacent hoops secured to one another.

[0131] First, referring to FIG. 22, straight stent 400 comprisesproximal stent portion (or segment) 401, distal stent portion 402, andan intermediate portion 403.

[0132] Proximal portion 401 is a ring formed of a number oflongitudinally spaced hoops 20 as described in connection with theformation of stent 10 above. In the illustrated embodiment, two hoops 20are used, each hoop 20 having a unit width.

[0133] Distal portion 402 is also a ring formed of longitudinallydisplaced hoops 20 in the manner described above. Distal ring 402 hastwo hoops 20 of unit width in the illustrated embodiment.

[0134] Intermediate portion 403 of straight stent 400 is formed ofbiocompatible woven fabric such as, for example, a plain woven fabricmade from 30 or 40 denier polyester. In this embodiment, intermediatefabric section 403 does not cover a stent. Fabric portion 403 isattached at its proximal and distal ends to the proximal and distalstent portions, respectively, by stitching, for example, with 0.003 inchpolypropylene filaments around apices 22 of the stent portions. Otherthan such connections at its longitudinal ends, intermediate fabricsection 403 is unsupported by any stent.

[0135] The second embodiment of a straight stent that may be usedaccording to this invention is illustrated in FIG. 23. Straight stent450 includes stent portion 451, constructed of wire loops as describedabove with reference to stent portions 401 and 402. Stent portion 451 ispartially covered by fabric 452. In this embodiment, fabric portion 4S1covers and is supported by stent 451, whereas with stent 400, the fabricportion 403 is not supported by a stent.

[0136] To treat an abdominal aortic aneurysm that does not extend downover the walls of the iliac arteries, as shown in FIG. 24(a), straightstent 400 (or 450) is disposed as illustrated in FIG. 26. Proximal stentportion 401 engages the inner walls of the aorta above the aneurysm.Distal stent portion 402 engages the inner wall of the aorta below theaneurysm. Intermediate fabric portion 403 extends across the aneurysm,providing a strong, stable lumen for blood flow through the aorta.

[0137]FIG. 28 illustrates the delivery apparatus used to implantstraight stent 400 in the vasculature. This apparatus is very similar tothat described above for the delivery system to be used with thebifurcated stent or prosthesis. Accordingly, like reference numeralsrefer to the same components.

[0138] In the introducer 410 shown in FIG. 28, proximal portion pusher102 engages proximal stent portion 401. Distal portion pusher 103engages distal stent portion 402.

[0139] In use, straight stent 400 is first charged into the introducerby cooling it to temperatures below 10° C., radially compressing it, andinserting it within outer sheath 101, as described above in connectionwith the bifurcated stent or prosthesis. The remainder of introducer 410is also assembled as described in connection with introducer 100.

[0140] Introducer 410 is passed through an entry point (not shown) overguide wire 411 as shown in FIG. 24(a). This insertion may beaccomplished using percutaneous or cut-down techniques. Introducer 410is then inserted to the desired delivery location.

[0141] In the aorta, introducer 410 is positioned and balloon 107 isinflated above the renal arteries in the same manner as described abovein connection with the bifurcated stent and as illustrated in FIG.24(a).

[0142] While maintaining proximal portion pusher 102 in a fixedposition, outer sheath 101 is withdrawn until proximal portion 401 ofstent 400 emerges from outer sheath 101 as shown in FIG. 24(b). Using aradiopaque marker 420 disposed on the proximal end of the proximalportion 401, stent 400 is optimally aligned within the aorta. Outersheath 101 is further withdrawn until proximal portion 401 emergestherefrom, as shown in FIG. 25. Outer sheath 101 is then furtherwithdrawn until it is flush with proximal portion pusher 102. Then bothouter sheath 101 and proximal portion pusher 102 are withdrawn whilemaintaining distal portion pusher 103 in a fixed position. Distalportion 402 is thus deployed from the end of outer sheath 101, as shownin FIG. 26.

[0143] Balloon 107 is then deflated and withdrawn inside proximalportion 401 where balloon 107 is reinflated to seat the stent 400, asshown in FIG. 27. Balloon 107 is then withdrawn, along with theintroducer 410 as described above, and the entry point is closed.

[0144]FIG. 29 illustrates the apparatus used to deploy straight stent450, shown in FIG. 23, of the present invention. This apparatus is verysimilar to that described above for the delivery system to be used withthe bifurcated stent or prosthesis. Accordingly, like reference numeralsrefer to the same components.

[0145] Proximal portion pusher 102 in this embodiment is glued to distalportion pusher 103 such that ends 115 and 116 are flush. These flushends are adapted to engage stent 450 within outer sheath 101.

[0146] In use, straight stent 450 is first charged into introducer 490by cooling it to temperatures below 10° C., radially compressing it, andinserting it within outer sheath 101, as described above in connectionwith the bifurcated stent or prosthesis. The remainder of introducer 490is also assembled as described in connection with introducer 100.

[0147] Introducer 490 is passed through an entry point (not shown) overa guide wire 411 as shown in FIG. 30. This insertion may be accomplishedusing percutaneous or cut-down techniques. Introducer 490 is theninserted to the desired delivery location.

[0148] In the aorta, introducer 490 is positioned and balloon 107 isinflated above the renal arteries in the same madder as described abovein connection with the bifurcated stent and as illustrated in FIG. 31.

[0149] While maintaining attached proximal portion pusher 102 and distalportion pusher 103 in a fixed position, outer sheath 101 is withdrawnuntil proximal portion 451 of stent 450 emerges from outer sheath 101 asshown in FIG. 32. Using a radiopaque marker 420 disposed on the proximalend of the proximal portion 451, stent 450 is optimally aligned withinthe aorta. Outer sheath 101 is then completely withdrawn until stent 450is deployed into the aorta as shown in FIG. 33.

[0150] Balloon 107 is then deflated and withdrawn inside proximalportion 451 where balloon 107 is reinflated to seat the stent 450, asshown in FIG. 34. Balloon 107 is then withdrawn, along with theintroducer 490 as described above, and the entry point is closed.

[0151] The angeological disease of occlusion is the blockage of anartery resulting from a buildup or clot of soft thrombus. There are twotypes of occlusions that can occur at the aorta-iliac bifurcation. Thefirst is infrarenal occlusion. In this case, the blockage extends in theaorta from just below the renal arteries into the iliac arteries. Thesecond type is an occlusion that is limited to the immediate area of thebifurcation.

[0152] To treat an infrarenal occlusion, a canalization is first madethrough the thrombus by methods known in the art. A bifurcatedendoluminal prosthesis according to the present invention is thenimplanted at the bifurcation site to provide an unobstructed lumenextending from the aorta into each of is the iliac arteries. Blood canthus flow freely from the aorta to the iliac arteries.

[0153] The bifurcated endoluminal prosthesis according to the presentinvention that is used to treat an occlusion must be fabric covered.This is necessary to prevent embolization from the thrombus remaining onthe wall of the recanalized artery.

[0154] An occlusion at the bifurcation is treated by recanalizing theartery as above. A bifurcated endoluminal prosthesis according to thepresent invention may be implanted at the bifurcation. Because theocclusion is limited to the immediate bifurcation site, however, theproximal portion of the prosthesis may be shorter than that discussedabove.

[0155] To implant the bifurcated endoluminal prosthesis to treat bothtypes of occlusion, the delivery 5 system comprising introducer 100discussed above for delivering the bifurcated endoluminal prosthesis totreat an abdominal aortic aneurysm is used. The same delivery methoddiscussed above for implanting the bifurcated endoluminal prosthesis totreat abdominal aortic aneurysms is used to implant the device to treatthe occlusion.

[0156] Using the method and apparatus of this invention to treatocclusion provides an unobstructed lumen through which blood can flowfrom the aorta to the iliac arteries.

[0157] The angeological disease of stenosis is a narrowing of an arterycaused by a buildup of hard calcified plaque. This is usually caused bya buildup of cholesterol. To treat such an angeological disease,angioplasty is performed on the plaque according to methods well knownin the art. The bifurcated endoluminal stent according to the presentinvention is then implanted at the bifurcation site. This stent is thesame as that described above for treatment of an abdominal aorticaneurysm. To treat the stenosis, however, it is not necessary to coverthe stent with a fabric, thus creating a Prosthesis. Because restenosisis rare at the bifurcation site, there is no need to isolate the bloodflowing in the lumen from the walls of the arteries.

[0158] The delivery system used to implant the bifurcated endoluminalstent used to treat stenosis is the same as that illustrated in FIG. 8except that balloon 107 is not required. Because there is no fabricaround the stent to be affected by blood flow in the arteries and causemigration of the bifurcated stent, it is not necessary to block theblood flow with the balloon. Otherwise, the delivery system forimplanting the bifurcated stent to treat stenosis is the same as thatfor implanting the bifurcated prosthesis to treat abdominal aorticaneurysm.

[0159] Similarly, with the exception of the steps involving inflation ofballoon 107 to block blood flow, the method of delivering the bifurcatedendoluminal stent to treat stenosis is the same as that described abovefor delivering the bifurcated endoluminal prosthesis to treat abdominalaortic aneurysm.

What is Claimed:
 1. An introducer for delivering, into the vasculatureat an angeological bifurcation where a blood vessel branches into twobranched vessels, a bifurcated endoluminal stent or prosthesis having aproximal portion adapted to be disposed in said blood vessel and adistal portion adapted to be disposed at least partially in one of saidtwo branched vessels, said introducer comprising: (a) a tubular outersheath; (b) a proximal portion pusher disposed at least partially withinsaid outer sheath; and (c) a distal portion pusher disposed at leastpartially within said proximal portion pusher.
 2. An introducer fordelivering a bifurcated endoluminal stent or prosthesis as claimed inclaim 1 further comprising a balloon catheter, having a balloon attachedthereto, disposed at least partially within said distal portion pusher.3. An introducer for delivering a bifurcated endoluminal stent orprosthesis as claimed in claim 2 further comprising a hemostasis valveattached to the distal end of said distal portion pusher.
 4. Anintroducer for delivering a bifurcated endoluminal stent or prosthesisas claimed in claim 2 further comprising wings on said outer sheath andsaid proximal portion pusher.
 5. An introducer for delivering abifurcated endoluminal stent or prosthesis as claimed in claim 2,wherein said balloon catheter has an injection orifice and an injectionconduit therein.
 6. An introducer for delivering a bifurcatedendoluminal stent or prosthesis as claimed in claim 2, wherein saidballoon catheter has an inflation orifice and an inflation conduittherein.
 7. An introducer for delivering a bifurcated endoluminal stentor prosthesis as claimed in claim 2, wherein said balloon catheter has aproximal end with a nose cone attached thereto.
 8. An introducer fordelivering into the vasculature at an angeological bifurcation where ablood vessel branches into two branched vessels, an endoluminalprosthesis having a proximal stent portion and a distal stent portion,said introducer comprising: (a) a tubular outer sheath; (b) a proximalportion pusher disposed at least partially within said outer sheath andhaving a proximal end adapted to contact said proximal stent portion;(c) a distal portion pusher disposed at least partially within saidproximal portion pusher and having a proximal end adapted to contactsaid distal stent portion; and (d) a balloon catheter, having a balloonattached thereto, disposed at least partially within said distal portionpusher.
 9. An introducer for delivering an endoluminal stent into thevasculature at an angeological bifurcation where a blood vessel branchesinto two branched vessels, said introducer comprising: (a) a tubularouter sheath; (b) a proximal portion pusher disposed at least partiallywithin said outer sheath and having a proximal end adapted to contact adistal end of said stent; and (c) a distal portion pusher disposed atleast partially within said proximal portion pusher and secured to saidproximal portion pusher such that proximal ends of said distal portionpusher and said proximal portion pusher are flush with one another. 10.A method for delivering a bifurcated endoluminal stent or prosthesishaving a proximal portion and a first distal portion into thevasculature at an angeological bifurcation where a blood vessel branchesinto a first branched vessel and a second branched vessel, said methodcomprising the steps of: (a) inserting a first introducer containingsaid stent or prosthesis into the vasculature to a predetermineddelivery location, said first introducer comprising an outer sheath, aproximal portion pusher, and a distal portion pusher; (b) withdrawingsaid outer sheath of said first introducer while maintaining saidproximal portion pusher in a fixed position until said proximal portionof said stent or prosthesis is deployed from said first introducer intosaid blood vessel; (c) withdrawing said outer sheath and said proximalportion pusher while maintaining said distal portion pusher in a fixedposition until said first distal portion of said stent or prosthesis isdeployed from said first introducer at least partially into said firstbranched vessel; and (d) withdrawing said first introducer from thevasculature.
 11. A method for delivering a bifurcated endoluminal stentor prosthesis as claimed in claim 10 further comprising the steps of:(a) inserting into the vasculature a second introducer containing asecond distal portion of said stent or prosthesis and comprising anouter sheath and a pusher; (b) withdrawing said outer sheath of saidsecond introducer while maintaining said pusher of said secondintroducer in a fixed position until said second distal portion of saidstent or prosthesis is deployed from said second introducer such that aproximal end of said second distal portion securely connects to saidproximal portion of said stent or prosthesis, and such that a distal endof said second distal portion extends at least partially into saidsecond branched vessel; and (c) withdrawing said second introducer fromthe vasculature.
 12. A method for delivering a bifurcated endoluminalstent or prosthesis as claimed in claim 10 wherein said first introducerfurther comprises a balloon catheter having a balloon attached theretoand said method further comprises the step of inflating said balloon toat least partially block blood flow in said blood vessel after insertingsaid first introducer into the vasculature.
 13. A method for delivering,into the vasculature at an angeological bifurcation where a blood vesselbranches into two branched vessels, an endoluminal prosthesis having aproximal stent portion, and a distal stent portion, said methodcomprising the steps of: (a) inserting an introducer containing saidprosthesis into the vasculature to a predetermined delivery location,said introducer comprising an outer sheath, a proximal stent portionpusher, a distal stent portion pusher, and a balloon catheter having aballoon attached thereto; (b) inflating said balloon to at leastpartially block blood flow in said blood vessel; (c) withdrawing saidouter sheath of said introducer while maintaining said proximal stentportion pusher in a fixed position until said proximal stent portion ofsaid prosthesis is deployed from said introducer into said blood vessel;(d) withdrawing said outer sheath and said proximal stent portion pusherwhile maintaining said distal stent portion pusher in a fixed positionuntil said distal stent portion of said prosthesis is deployed from saidintroducer into said blood vessel; and (e) withdrawing said introducerfrom the vasculature.
 14. A method of treating an angeological diseaseat a bifurcation site where a blood vessel branches into a firstbranched vessel and a second branched vessel comprising the steps of:(a) disposing in said blood vessel a proximal portion of an endoluminalstent; (b) directing blood flow from said blood vessel into said firstbranched vessel through a first distal portion of said endoluminalstent, said first distal portion being connected to said proximalportion and extending into said first branched vessel; and (c) directingblood flow from said blood vessel into said second branched vesselthrough a second distal portion of said endoluminal stent, said seconddistal portion being connected to said proximal portion and extendinginto said second branched vessel.
 15. A method of treating anangeological disease at a bifurcation site where a blood vessel branchesinto a first branched vessel and a second branched vessel as claimed inclaim 14 wherein said disease is stenosis.
 16. A method of treating anangeological disease at a bifurcation site where a blood vessel branchesinto a first branched vessel and a second branched vessel as claimed inclaim 14 that further comprises covering any of said proximal portion,said first distal portion, and said second distal portion with fabric.17. A method of treating an angeological disease at a bifurcation sitewhere a blood vessel branches into a first branched vessel and a secondbranched vessel as claimed in claim 16 wherein said disease is ananeurysm.
 18. A method of treating an angeological disease at abifurcation site where a blood vessel branches into a first branchedvessel and a second branched vessel as claimed in claim 16 wherein saiddisease is an occlusion.
 19. An endoluminal stent comprising a pluralityof hoops which are axially displaced in a tubular configuration along acommon axis, each of said hoops (a) being formed by a substantiallycomplete turn of a sinuous wire having apices, and (b) having acircumference that lies in a plane substantially perpendicular to thelongitudinal axis of said stent; wherein apices of adjacent hoops arejuxtaposed to one another, and at least two juxtaposed apices areconnected by a securing means.
 20. A stent as recited in claim 19 incombination with one or more additional stent segments.
 21. A stent asrecited in claim 20 wherein at least one of said additional stentsegments comprises a plurality of hoops which are axially displaced in atubular configuration along a common axis, each of said hoops (a) beingformed by a substantially complete turn of a sinuous wire having apices,and (b) having a circumference that lies in a plane substantiallyperpendicular to the longitudinal axis of said stent; wherein apices ofadjacent hoops are juxtaposed to one another, and at least twojuxtaposed apices are connected by a securing means.
 22. A stent asrecited in claim 20 wherein said one or more additional segments areaxially aligned with one another.
 23. A stent as recited in claim 20wherein said one or more additional segments are secured to one anotherby connecting means connecting at least some of the apices of hoops atmating ends of said stent and said additional segments.
 24. A stent asrecited in claim 20 wherein adjacent hoops are of the same diameter. 25.A stent as recited in claim 20 wherein adjacent hoops are of a differentdiameter.
 26. A stent as recited in claim 22 wherein said axiallyaligned segments are connected to one another by a tubular fabricelement.
 27. A stent as recited in claim 20 wherein a first additionalsegment is axially parallel to, but non-common co-axial with, saidstent.
 28. A stent as recited in claim 27 further comprising a secondadditional segment axially parallel to said stent, but non-co-axial witheither said stent or said first additional stent segment.
 29. A stent asrecited in claim 28 wherein at least one of said additional stentsegments is of frustoconical shape and is further combined with anadditional stent segment, one end of which includes a matingfrustoconical shape.
 30. At stent as recited in claim 29, wherein saidmating frustoconical stent segments are adapted to be separately placedin a bifurcated artery and then, by expansion of one of saidfrustoconical stent segments, secured to one another
 31. An endoluminalstent as claimed in claim 19 wherein said hoops are formed of a singlecontinuous wire.
 32. An endoluminal stent as claimed in claim 19 whereinsaid securing means is a suture.
 33. An endoluminal stent as claimed inclaim 32 wherein said suture is a tied loop of thermoplastic material.34. An endoluminal stent as claimed in claim 19 wherein said securingmeans is a ring.
 35. An endoluminal stent as claimed in claim 19 whereinsaid securing means is a staple.
 36. An endoluminal stent as claimed inclaim 19 wherein said securing means is wire twisted into loop.
 37. Anendoluminal stent as claimed in claim 36 wherein said wire is nitinol.38. An endoluminal stent as claimed in claim 19 wherein said securingmeans is bead of thermoplastic material.
 39. An endoluminal stent asclaimed in claim 19 wherein the plane of the circumference at eachlongitudinal end of the stent is square to the longitudinal axis of thestent.
 40. An endoluminal stent as claimed in claim 19 wherein saidstent is at least partially covered in fabric.
 41. An endoluminal stentas claimed in claim 31 wherein said wire is nitinol.
 42. A method ofmaking an endoluminal stent having a plurality of hoops which areaxially displaced in a tubular configuration, each of said hoops beingformed by a substantially complete turn of a sinuous wire with apicesand having a circumference that lies in a plane substantiallyperpendicular to the longitudinal axis of the stent, said methodcomprising the steps of: (a) winding a wire in a zig-zag pattern arounda mandrel having a plurality of upstanding pins defining said zig-zagpattern to form a first hoop having apices and a circumference that liesin a plane substantially perpendicular to the longitudinal axis of saidmandrel; (b) longitudinally displacing said wire with respect to theaxis of said mandrel; (c) winding said wire in a zig-zag patter: arounda plurality of upstanding pins on said mandrel to form a second hoop,adjacent said first hoop, having apices juxtaposed to the apices of saidfirst circumferential hoop and a circumference that lies in a planesubstantially perpendicular to the longitudinal axis of said mandrel;(d) longitudinally displacing said wire with respect to the axis of saidmandrel; (e) repeating steps (a)-(d) to form additional hoops until apredetermined number of hoops are formed; (f) annealing said wire onsaid mandrel; (g) cooling said wire on said mandrel; (h) removing saidwire from said mandrel; and (i) securing together at least twojuxtaposed apices of adjacent hoops.
 43. An endoluminal stent comprisinga radiopaque marker disposed on at least one end of the stent.
 44. Anendoluminal stent as claimed in claim 43 wherein said radiopaque markercomprises a radiopaque element attached to one end of said stent.
 45. Anendoluminal stent as claimed in claim 44 wherein said element is aplatinum wire.
 46. An endoluminal stent as claimed in claim 44 whereinsaid element is a gold wire.
 47. An endoluminal stent as claimed inclaim 43 wherein said radiopaque marker comprises a radiopaque tubedisposed around a part of said stent.
 48. An endoluminal stent asclaimed in claim 47 wherein said tube is platinum.
 49. An endoluminalstent as claimed in claim 47 wherein said tube is gold.
 50. A bifurcatedstent for use in juxtaposition with an angeological bifurcationcomprising a proximal stent portion adapted to be disposed within ablood vessel in juxtaposition with a bifurcation, a first distal stentportion adapted to extend across the bifurcation into one of thebranched blood vessels, and a second distal stent portion adapted toallow blood to flow from the proximal portion into the other branchedvessel and, at least one barb extending radially outward from any ofsaid proximal stent portion, said first distal stent portion, and saidsecond distal stent portion.
 51. Apparatus for delivering an endoluminalstent or prosthesis into the vasculature comprising: (a) an introducerhaving a on a distal end thereof; and (b) a cartridge having an innertubular member containing said stent or prosthesis in a compressedstate, an outer sheath, and a second portion of said lock fitting;wherein said first portion of said lock fitting on said introducer mateswith said second portion of said lock fitting on said cartidge toprevent relative movement of said introducer and said cartridge. 52.Apparatus as claimed in claim 51 wherein said lock fitting is a Luerlock.
 53. Apparatus as claimed in claim 51 further comprising ahemostasis valve on said introducer and a pusher adapted to push saidcompressed stent or prosthesis through said cartridge, through saidintroducer, and into the vasculature.